French bourbe 'sludge' (updated)

French bourbe 'sludge' (collective form bourbier) designates a kind of dark, thick mud deposited by stagnant or waste waters and surely derives from Gaulish *borwā (f.), whose supposed meaning 'hot, boiling spring' accroding to standard dictionaries, which link it to Welsh berwi, Breton bervi 'to boil'^1. 

However, in my opinion this etymology is semantically unsatisfactory, and I'd prefer a substrate loanword from Baltic *purwā > Lithuanian pũrva 'smudge, dregs', Latvian pùrvs, purve 'morass, swamp', a word with parallels in Indo-Aryan: Sanskrit púrīṣa- 'crumbling or loose earth, rubbish; feces, excrement, ordure', Sinhalese puraṇa 'fallow or waste land'. 
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¹ X. Delamarre (2008): Dictionnaire de la langue gauloise, pp. 82-83.

Gaulish *komboro- 'heap, accumulation' (updated)

Basque gonburu (B), bonburu (B) 'excess', usually derived from Latin cumulu- 'heap', is actually loanword from Gallo-Romance *komboro- 'heap, accumulation'¹ (REW 2075). This is the origin of Medieval Latin combrus 'abatis' (an obstacle formed by a row of tree branches pointing to the enemy) and Old French combre 'dam on a river'. Other derivatives, we we've also got French encombrer, Italian ingombrare 'to obstruct, to block' < *in-comb(o)rāre and Spanish escombrar 'to disembarrass' < *ex-comb(o)rāre. 

Although specialists usually give this word a Celtic etymology from Celtic *kom-bero-² >Old Irish commar, Welsh cymer, Breton kemper (hence the toponym Quimper) 'confluence (of rivers)', in my opinion this etymology is semantically unsatisfactory,  so I'd prefer a substrate loanword related to Baltic *kumb(u)r- 'soil elevation, hill' (Lithuanian kumbrī̃s, kum̃bris, Latvian kumburis) and Thracian skumbras (ancient toponyms Skóumbros, Skoũmbro)³. As the source language (either from the Baltic group or a close relative of it), had no differentiated /a, o/ vowels but only /a/, its /u/ was actually realized [ʊ] and therefore was interpreted by Celtic (Gaulish) speakers as being closer to their own /o/⁴.

Working independently of each other, the Catalan linguist Joan Coromines and the Spanish Indo-Europeanist Francisco Villar apparently conflated this Baltoid language with a different Italoid (i.e. akin to Italic) one, called Sorothaptic by Coromines from its purported association with the Urnfield culture, attested in several lead foil inscriptions (written in Latin alphabet) found at the beggining of the 20th century in the thermal station of Amélie-les-Bains/Els Banys d'Arles (Rosselló)⁵. These are votive texts addressed to some water deities (nymphs) referred to as kantas niskas, where kantas presumably derives from IE *k´wen-to- 'holy' and niskas could be related to Basque neska 'unmarried girl'.

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¹ A meaning proposed by Coromines instead of Meyer-Lübke's original one. 
² X. Delamarre (2008): Dictionnaire de la langue gauloise, p. 122. 
³ I. Duridanov (1969): Die Thrakisch- und Dakisch-Baltischen Sprachbeziehungen, p. 93.
⁴ Villar has an idiosyncratic theory of the development of the 5 vowel system of some IE languages (e.g. Italic, Celtic, Greek) from an older 4 vowel system /i, ε, ɑ, ʊ/ found in e.g. Anatolian, Balto-Slavic, Germanic, as well as in Etruscan. See F. Villar (2000): Indoeuropeos y no indoeuropeos en la Hispania prerromana, pp. 369-378.
⁵ J. Coromines (1976): Els ploms sorotàptics d'Arles, in Entre dos llenguatges (II), pp. 142-216. Lusitanian, a language attested on several inscriptions written in the Latin alphabet, would also belong to this group.

Greek kédros 'cedar', Latin citrus 'thuja; citron'

As most terms related to Mediterranean flora, Greek kédros 'cedar' (borrowed into Latin cedrus) has no IE etymology. There're also the derivatives kédris, kédron 'juniper berry' (actually a modified conifer cone).

On the other hand, Latin citrus, which designates two different kinds of tree, 'thuja' (citrum 'thuja wood') and 'citron'¹, is somehow related to the Greek word, possibly through an Etruscan intermediate².

In my opinion, these are instances of a Wanderwort of Semitic origin: *kˁtr- 'smoke, incense', referring to the aromatic characteristics of these trees, either the wood (cedar, thuja) or the fruit (citron). 

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¹ Whose Greek names kítron, kítrion, kítrea, are seemingly loanwords from Latin.
² A. Ernout & A. Meillet (1959): Dictionnaire étymologique de la langue latine, pp. 123-124.

Greek parthénos 'virgin, unmarried girl' (updated)

Goddess Britomartis

Greek parthénos 'virgin, unmarried girl' is an interesting word with no clear Indo-European etymology, although the German Indo-Europeanist Gert Klingenschmitt¹ has proposed a derivation from *pr̥-sténos '(having) protunding breasts', a compound of *pr̥- 'before' and *sténos 'breast' (Avestan fštāna-) < IE *psten(o)- parallel to Avestan ərəduua-fšnī- 'having firm breasts'.

Despite being accepted by some specialists², to me this proposal is phonetical and semantically implausible, so I regard this word as a kinship term with parallels in Old Prussian mārtin, mārtan 'bride', Lithuanian martì ‘bride, daughter-in-law’, Latvian mā̀rša 'brother's wife', Crimean Gothic marzus ‘wedding’, apparently a Wanderwort found in Eteocretan *marti-/*marpi- 'virgin/maiden' (cfr. the Goddess Britomartis 'Sweet Virgin/Maiden'), Etruscan marθ 'bride' (in papac marθc svlisva 'the wills of the grandfather and the bride')³, and ultimately related to East Caucasian (Nakh-Daghestanian) *bHaddɮi (~ -ǝ-) 'young (of animals)'⁴. 

In my opinion, this is the likely source of Sanskrit pr̥̥thuka- 'calf, young of an animal', Armenian ort^c 'young of cattle or deer' and Greek pórtis 'calf, young heifer', pórtaks 'calf'⁵, linked by Thomas Burrow⁶ to parthénos. The semantic shift from 'heifer' to 'virgin, unmarried girl' would be explained in the context of a pastoralist society like those of Kurgan people. 

Also related within IE would be Germanic *farzá-, *farzḗn, *fársō(n) 'bull, ox' and Slavic *porsъ 'bull'. In turn, the Caucasian word has cognates in Proto-Altaic *bāla 'child, young' and PIE *pelH- 'foal' (Greek pôlos 'foal', Armenian ul 'kid, young of deer or gazelle', Albanian pelë 'mare')⁷.

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¹ G. Klingenschmitt (1974): 'Grieschisch παρθένος', in Antiquititae Indogermanicae. Gedenkschrift für Hermann Güntert, pp. 273-278. 
² R.S.P. Beekes (2010): Etymological Dictionary of Greek, p. 1153. See also X. Delamarre (2008): Gauloises Ardasina, Titiluxsa, Uxesina, grec parthénos, avestique ərəduuafšnī-. Une dénomination indo-européenne de la jeune femme: 'celle qui ha les seins hauts'.
³ A. Morandi (1987): La tomba degli Scudi di Tarquinia [Contributo epigrafico per l'esegesi dei soggetti], in Mélanges d'École française de Rome. Antiquité, p. 104.
⁴ Diakonoff-Starostin link to this Hurrian pōra-(m)mi, Urartian porā 'slave'. See I. Diakonoff & S. Starostin (1986): Hurro-Urartian as an Eastern Caucasian Language, §2.
⁵ Also related are Old Church Slavonic za-prъtъkъ 'wind egg', Czech s-pratek 'premature calf' (Pokorný).
⁶ T. Burrow (1955): The Sanskrit Language, p. 71. 
⁷ J. Mallory & D. Adams (2006): The Oxford Introduction to PIE and the PIE world, p. 192.

Furnée and the Pre-Greek substrate (updated)

In order to characterize Pre-Greek loanwords in his own Etymological Dictionary of Greek (2010)¹, the Dutch Indo-Europeanist Robert Beekes used his compatriot Edvard Furnee's PhD disertation Die wichtigsten konsonantischen Erscheinungen des Vorgriechischen (1972), a pioneer work later followed by Vorgriechisch-Kartvelisches. Studiem zum ostmediterranen Substrat nebst einem Versuch zu einer neuen pelasgischen Theorie (1979) and Paläokartvelisch-pelasgische Einflüsse in den indogermanischen Sprachen. Nachgewiesen anhand der spätindogermanisch-griechischen Reflexe urkartvelischer Sibilanten und Affrikanten (1986).

In these later works (thoroughly ignored by Beekes²), Furnee develops the theory Pre-Greek/Pelasgian was a Paleo-Kartvelian (an older stage than Proto-Kartvelian) language. For example, Greek kháos 'abyss, chasm'³ < Pre-Greek *kʰáw- can be linked to PK *qew-/*qaw- 'ravine' (Old Georgian qev-i, qev-n-i, Georgian xev-i, Megrel xab-o)⁴, where PK q ~ Pre-Greek kʰ'⁵.

In my opinion, these and other correspondences between Pre-Greek and Kartvelian would be evidence of language contact rather than a genetic relationship⁶, as they include borrowings into the opposite direction. For example, although PK *tor- (Georgian tor-i, torn-i 'harness, armour')⁷ corresponds to Greek thôraks (Ionic thôrēks, Mycenean TO-RA-KE) 'cuirass; trunk, chest'⁸ < Pre-Greek *tʰur-āk-, it's clear the source can't be Paleo-Kartvelian.

This would be an Eurasiatic root found in Latin corium 'skin, hide, leather', cortex 'bark, shell', Sanskrit cárman-, Avestan čarǝman- < PIE *s-ker- 'bark, skin'⁹, PK *tser- (Laz cara) 'rough infertile earth', Proto-Uralic *tɕarV 'hard', Proto-Altaic *tSarV 'snow, snow crust', Proto-Dravidian *tSara- 'rough on surface', and whose protoform is reconstructed by Dolgopolsky as *tɕ(ˀ)arV/*tsˀarV 'hard/firm, hardened crust, hard surface' (ND 311). The initial sibilant affricate was centumized into a velar stop¹⁰ (palatalized in Indo-Iranian) in IE but it gave a dental stop in Pre-Greek.
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¹ Which is part of the so-called Indo-European Etymological Dictionaries Online (IEDO) project, a series of etymological dictionaries of IE languages edited by Alexander Lubotsky from Leiden University. Until some years ago, preliminary versions of them were available online for free under the label Indo-European Etymological Dictionary (IEED), but unfortunately now they are of restricted access, as copyright is owned by publisher Brill. 
² He regards Pre-Greek as a uniform non-IE language "with no recognizable cognates", thus ignoring most recent research on the subject. 
³ On the other hand, the related kháũnos 'slack, porous; vain, frivolous' < Pre-Greek *kʰáw-n-o- derives from a suffixed variant of the same root. Beekes' allusion to a possible parallel in Germanic and Baltic 'palate' is totally ungrounded. See R.S.P. Beekes (2010), op. cit., p. 1614.
⁴ E.J. Furnée (1979), op. cit., §57.
⁵ Notice, however, the possible link (already observed in Varro's De lingua latina) between the Greek word and Latin cavus 'hollow' < PIE *kouH-o- by Thurneysen-Havet's Law. See L. Horton-Smith (1895): Establishment and Extension of the Law of Thurneysen and Havet, The American Journal of Philology, 16, pp. 444-467.
⁶ In fact, the Kartvelianist and Indo-Europeanist Thomas Gamkrelidze accepted some of Furnée's correspondences, relating them to the argonauts. See T.V. Gamkrelidze & V.I. Ivanov (1995): Indo-European and the Indo-Europeans, p. 799-804.

⁷ E.J. Furnée (1979), op. cit., §16.

⁸ R.S.P. Beekes (2010), op. cit., p. 569.
⁹ Please notice Greek kôrykos 'leather sack' is unrelated. See R.S.P. Beekes (2010), op. cit., p. 816.
¹⁰ Not *sk- as thought by Nostraticists, because *s- (called "s-mobile" in the literature) is a fossilized prefix.